[postgis-users] Creating trajectory/lines from millions of points[PostGIS]

[Hugues François]

Hello,

 

In your case I would have try to make multilines for each taxi and each status (i.e. two multi by taxi) and then dump them into  simple linestrings. All in a query that may look like this assuming you have a taxi id field:

 

WITH multis AS (

                SELECT id, status, ST_MakeLine(array_agg(point_geom )) AS mylines

                FROM your_table

GROUP BY id, status

ORDER BY time_field

)

 

SELECT id, status, (ST_Dump(mylines)).geom

FROM multis

 

You may want to add a time reference to your lines. To do this, you can add an extraction from your timestamp field (e.g. day or month) and add it into the WITH and to the group by clause.

 

Hugues.

 

 

 

 

 

De : postgis-users-bounces at lists.osgeo.org [mailto:postgis-users-bounces at lists.osgeo.org] De la part de Oliver Burgfeld
Envoyé : mardi 25 novembre 2014 07:09
À : postgis-users at lists.osgeo.org
Objet : [postgis-users] Creating trajectory/lines from millions of points[PostGIS]

 

Hi,

I have millions of points in a PostGIS database containing taxi gps tracks. Now I want to create lines from these points by vehicleid and ordered by timestamp. But, and that's my problem right now, at first I want to include every column of my point table into the "line table" and I also need to intersect those lines at specific points.

I have one column representing the "taxi_is_occupied" status with 0 or 1. 

What I want now is to create lines which are divided every time this status changes. In the end I need lines which show the path of every taxi over time, divided every time the status of the car changes so that I can query all lines where the taxi is occupied, for example.

What do I have to use therefore? I know that there is the ST_MakeLines tool existing in PostGIS, but as I am a new PostGIS user... I do not know exactly how to use it to get the results I need. 

 

Thanks a lot

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